1. Field of the Invention
The present invention generally relates to an electronic still camera using a CCD (charge coupled device) of the frame transfer type.
The invention particularly relates to an electronic still camera in which a field signal produced from a CCD of the frame transfer type is converted into a signal equivalent to a storage frame and is recorded on a rotatable magnetic recording medium having a small diameter.
Further, the present invention also relates to a method of reading a still picture recorded on a magnetic disk.
More particularly, it relates to a method of reading a still picture in which a still picture is read by converting a reproduced signal obtained from noninterlace signal recorded according to sequential areas into an interlace signal which is suitable to be watched by a television receiver.
2. Background of the Invention
Generally, in the case where a CCD of the frame transfer type (hereinafter referred to as an FTCCD) is used for a movie, the FTCCD can produce a frame signal having vertical picture elements, the number of which is equal to that of TV scanning lines through 2:1 interlace-scanning.
On the other hand, in the case where such an FTCCD as described above is applied to an electronic still camera to pick up a still picture, only a field signal of one scene can be obtained as an output signal for one shot. Therefore, there has been such a disadvantage that the original resolution of the FTCCD cannot be sufficiently utilized.
In order to eliminate the foregoing disadvantage, there has been proposed a system in which a signal charge is transferred from a CCD light reception section to a CCD storage section a single time in a very short period during one shot exposure to thereby make it possible to utilize a picture signal of two fields for the formation of a reproduced picture. In this system, although the exposure is continued during this signal charge transfer period, the transfer period is significantly shorter than the exposure period. Therefore, the picture quality is not degraded so much even though light reception elements of the CCD light reception section which are transferring the signal charge are irradiated so that a signal charge corresponding to a displaced image is superimposed on that to be transferred.
In the foregoing system, however, when the exposure period cannot be established to be sufficiently long relative to the extremely short transfer period, for example, when a high-speed shutter is applied to the system, there is a possibility that the exposure during the transfer period exerts a deleterious influence on the picture quality.
On the other hand, the inventors of this application have proposed a solid state image pickup element which can produce, in sequence for the red, green and blue (R, G, B) areas, a picture signal obtained by imaging a subject. They have also proposed an electronic still camera in which a picture signal is recorded on a magnetic disk having a small diameter by using this solid state image pickup element.
FIG. 1 is a diagram for explaining the foregoing solid state image pickup element and electronic still camera.
In a solid state image pickup element 10, microcolor filters (represented by symbols R, G, and B in the drawing) are arranged not only on a photoelectric conversion section 12 but also on a vertical transfer line 11 of a conventionally known CCD of the interline transfer type. This dual placement of the micro-color filters thereby provides a photoelectric conversion function also in the vertical transfer line 11. Signal charges stored in the vertical transfer line 11 and in the photoelectric conversion portion 12 are output in the area sequence of R, G, and B from a buffer amplifier 14 through a single horizontal CCD 13.
In the electronic still camera to which this solid state image pickup element 10 is applied, picture signals obtained by picking up a subject and output in area sequence are distributed to three magnetic heads 16 respectively corresponding to three colors R, G, and B through an area change-over or demultiplexer circuit 1. Thereby, the three magnetic heads 16 magnetically record the picture signals on three corresponding tracks of a magnetic disk 17.
Reproduction is performed in such a manner that the connection of a recording/reproducing change-over switch 18 is changed over to the reproducing side. Then, the three tracks are simultaneously reproduced by the three corresponding magnetic heads 16 used as reproducing heads to thereby provide, for example, a printed picture. Although the thus arranged electronic still camera is of the single plane type, the same color reproducing property and resolution can be obtained as in the case where an image pickup operation is performed by a camera of the three-plane type. Also, a clear color picture can be obtained because of an improved signal-to-noise (S/N) ratio. Further, being of the single plane type, the electronic still camera can be reduced in size as well as in weight.
Thus, the solid state image pickup element and the electronic still camera using the element have the foregoing superior features in comparison with the conventional ones. However, there has been an inconvenience in the case where a reproduced picture obtained by the electronic still camera is desired to be watched by an ordinary television system.
That is, there has been a disadvantage in that the area-sequential signal produced from the solid state image pickup element is a non-interlace signal which is recorded as a frame through full vertical scanning of all the scanning lines. However, a signal to be used in an ordinary television receiver is, as well known, an interlace signal obtained through interlace-scanning of the scanning lines. Therefore, the non-interlace signal is improper for such an ordinary television receiver.